IS 3400 (Part 9) :2003 ISO 2781:1988 - Indian Standard METHODS OF TEST FOR VULCANIZED RUBBER PART 9 RUBBER, VULCANIZED--DETERMINATION OF DENSITY (Second Revision ) ICS 83.060 0 BIS 2003 BUREAU MANAK OF BHAVAN, INDIAN STANDARDS ZAFAR MARG 9 BAHADUR SHAH NEW DELHI 110002 March 2003 Price Group 2 Rubber and Rubber Products Sectional Committee, PCD 13 NATIONAL FOREWORD This Indian Standard (Part 9) (Second Revision) which is identical with ISO 2781:1988 `Rubber, vulcanized -- Determination of density' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendations of the Rubber and Rubber Products Sectional Committee and approval of the Petroleum, Coal and Related Products Division Council. This standard was first published in 1967 aligning with ISO 2781:1975 `Determination of density of vulcanized rubbers' and revised in 1978. In the first revision, determination was made by observation of gravitational forces under different conditions, but for convenience, these forces were expressed in mass units. The Committee, therefore, decided to revise this standard to completely align with ISO 2781:1988. The text of ISO Standard has been proposed to be approved as suitable for publication as Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following: a) Wherever the words `International be read as `Indian Standard'. Standard' appear referring to this standard, they should b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker. and the relative humidity shall be taken as For tropical countries like India, the standard temperature 27* 2°C and 65 k 5 percent respectively. IS 3400 (Part 9) :2003 ISO 2781 :1988 lndian Standard METHODS PART 9 OF TEST FOR VULCANIZED RUBBER, VULCANIZED--DETERMINATION (Second RUBBER OF DENSITY Revision ) 1 Scope 4 Apparatus This International Standard specifies two methods of test for the determination of the density of solid vulcanized rubber. Such determinations are of importance in the control of the quality of a rubber compound and in the calculation of the mass of rubber required to produce a given volume of vulcanizate. This International Standard does not cover the determination of the relative density of rubber, which is the ratio of the mass of a given volume of the rubber to the mass of an equal volume of pure water at a given temperature. In this International Standard the determination is made by observation of gravitational forces under different conditions but, for convenience, these forces are expressed in mass units. Ordinary laboratory apparatus and 4.1 Analytical balance, accurate to 1 mg. 4.2 Balance pan straddle, of convenient size to support the beaker and permit determination of the mass of the teat piece in water (for method A). 4.3 Beaker, 250 cms capacity (or smaller if necessitated by the design of the balance) (for method A). 4.4 Density bottle (for method B). 2 Definition 5 Test piece For the purposes of this International Standard, the following definition applies. density: The mass of unit volume of the rubber at a stated temperature. It is expressed in megagrams per cubic metre (Mg/ms). 5.1 The teat piece shall consist of a piece of the rubbar with smooth surfaces, free from crevices and duet, and having a mass of at least 2,5 g. For method B the shape of the test piece shall be such as to permit cutting into suitable pieces (see 9.3). 5.2 A minimum of two teata shall be made. 3 Principle 6 ~me-interval testing between vulcanization and Two methods, A and B, are given. In method A the masses of the test piece in air and in water are determined using an analytical balance equipped with a pan straddle. The mass when immersed in water is less than that in air by the mass of water displaced, the volume of water displaced being equal to that of the test piece. Method B is intended to be used only when it is necessary to cut up the test piece into small pieces to eliminate air spaces, as in the case of narrow bore tubing and electric cable insulation. Measurements are made using a balance and a density bottle. Unless otherwise specified for technical reasons, the following requirements for time-intervals shall be observed. 6.1 For all teat purposes, the minimum vulcanization and testing shall be 16 h. time between 6.2 For non-product tests, the maximum time between vulcanization and testing shall be 4 weeks and for evaluations 1 IS 3400 (Part 9) :2003 ISO 2781 :1988 intended to be comparable, the tests, as far as possible, shall be carried out after the same time-interval. 6.3 For product tests, whenever possible, the time between vulcanization arid testing shall not exceed 3 months. In other cases, tests shall be made within 2 months of the date of receipt by the customer of the product. seconds to make sure that it does not drift gradually as a result of convection currents. NOTES 1 Where the filament usad has a mass lass than 0,010 g, such as is the case with thin nylon filament, the correction to account for its mess is not neceaee~ to ensure the statad sccuracy of the final result. However, when the teat pieca ia smaller than the ona apacifiad (e.g. when the density of small O-rings ia to be measured), this can lead to inaccuracies and the mess of tha filament naada to be tekan into account in the final calculation. If a maana of euspanaion othar than a filament is used, the volume and mass of the euapanaion must be taken into account in making the final calculation. 2 When this procedure is usad for rubbar having a density lees than 1 Mg/m3, a sinker is necessary; a furthar waighing of tha sinker alone in water is required. Alternatively, a Iiiuid of dtierent danaity to water may be used in place of the water, in which case the formulae givan in 10.1 are modified by the multiplication of the expression by the dansity of the liquid expressed in megagrama per cubic metre. 3 Tha main sources of error are a) air bubbles adhering to the surfaces of tha test pieca during weighings in water; b) surface tension effects on the filament; 7 Conditioning of test pieces 7.1 Samples and test pieces shall be protected from direct sunlight during the interval between vulcanization and testing. 7.2 Samples, after such preparation as is necessary, shall be conditioned at a standard temperature (that is, 23 `C f 2 `C or 27 `C t 2 `C) for at least 3 h before the test pieces are cut. These test pieces may be tested immediately but, if not, they shall be kept at the standard temperature until tested. If the preparation involves buffing, the interval between buffing and testing shall not axceed 72 h. 8 Temperature of test c) convection currents in the water in which the test piaca is suspended, to minimize which the temperature of the water and of the air in the balance case should be the same. 4 In order to minimize the adherence of air bubbles to the test piece, it is permissible either to add a trace (say 1 part in 10 000) of surface active material such as a detergent to the distilled water or to dip the test piece momentarily into a suitable liquid, such aa methyl alcohol or industrial methylated spirits, miscible with water and having a negligible swelling or leaching action on rubber. If the latter method is adopted, precautions should be taken to minimize the carry-over of alcohol. The test shall normally be carried out at a standard temperature (23 "C * 2 `C or 27 "C * 2 "C), the same temperature being used throughout one test or series of tests intended to be comparable. 9 9.1 Procedure Preparation of sample 9.3 If fabric is attachad to, or embedded in, the samples, it shall be Method B removed before cutting the test pieces. The method of removal shall preferably avoid the use of a swelling liquid, but, if necessary, a suitable non-toxic liquid of low boiling point may be used to wet the contacting surfaces. Care shall be taken to avoid stretching the rubber during the separation from the fabric, and the liquid, if used, shall be allowed to evaporate completely from the rubber surfaces after separation. Clothmarked surfaces shall be made smooth by buffing. 9.2 Method A Suspend the test piece (clause 5) from the hook on the balance (4. 1), using a suitable length of filament so that the bottom of the test piece is about 25 mm above the straddle (4.2). The filament shall be made from a material which is insoluble in water and which does not absorb a significant amount of water. It shall either be counterbalanced or be weighed and, if weighad, its maas shall be deducted from subsequent weighings of the test piece (see note 1). Weigh the test piece to the nearest milligram in air, Repeat the weighing with the test piece (and sinker, if required, see note 2) immersed in freshly boiled and cooled distilled water at a standard temperature (23 `C * 2 `C or 27 "C + 2 `C) contained in the beaker (4.3), placed on the straddle. Remove air bubblea adhering to the test piece (see note 4) and determine the mass to the nearest milligram, watching the pointer for a few Weigh the clean, dry density bottle and stopper (4.4) before and after the insertion of the test piece (clause 5) cut into suitable pieces. The exact size and shape of the pieces will depend on the thickness of the original test piece. They should be such that no two dimensions are greater than 4 mm and the third not greater than 6 mm. Within these limitations the pieces should be as large as possible. All cut edges shall be smooth. Fill the bottle, containing the rubber, coh-rpletely with freshly boiled and cooled distilled water at a standard temperature (23 "C * 2 `C or 27 `C * 2 "C). Remove air bubbles adhering to the rubber or to the walls of the bottle (see note 4 above). Insert the stopper, taking care that there is no air in the bottle or the capillary. Dry the outside of the bottle carefully. Weigh the bottle and contents. Empty the bottle completely and refill with freshly boiled and cooled distilled water. After removing the air bubbles, inserting the stopper and drying, weigh the bottle and water. Ail tha above weighinga shall be made to the nearest milligram. NOTE ­ Tha main source of error is air bubbles inside the botde. It may be neceeeery to heat the bottle and contants to approximately 50 "C to dislodga bubbles, but in this case the bottla and contante must be cooled before waighing, Alternatively, the bottla may be placed in a vacuum desiccator and the vacuum applied and released several times until no more air is extracted. 2 IS 3400 (Part 9): ISO 2781 :1988 2003 10 10.1 Expression of results Method A 10.2 Method B per cubic metre, is The density Q, expressed in megagrams given by the formula mz ­ m4­m3+m2­mj ml The density Q, expressed in megagrams per cubic metre, is given by the formula ml where ml ­ m2 ml m2 where ml is the net mass of the rubber; is the mass of the density bottle; is the mass of the density bottle plus test piece; mz is the mass of the rubber less the mass of an equal volume of water, determined by weighing in water, both at the standard temperature. This method is accurate to the nearest unit in the second place of decimals. The density of water at standard laboratory temperature be taken as 1,00 Mg/ms. NOTES 1 When a sinker has been used, the calculation must be modified as follows : Q= ml ml+m2­m3 where ml is the net ma= of the rubber; m~ is the mass of the density bottle plus test piece plus water; m4 is the mass of the density bottle filled with water. NOTE ­ For precise work, a factor to take account of the density of water at the test temperature should be used. may 11 Test report shall include the following particulars : The test report a) b) c) d) a reference to this International Standard; the mean density; the temperature of test; the method used (method A or method B); specified in this m2 is the mass of the sinker less the mass of an equal volume of water, determined by weighing in water; m3 is the mass of the sinker and rubber leas the mass of a volume of water equal to their combined volumes, determined by weighing in water. 2 For precise work, a factor to take account of the density of water at the test temperature should be usad. e) anv deviations from the procedure lnterna~onal Standard. 3 Bureau of Indian Standards BIS is a statutory harmonious institution established under the Bureau of Mian of standardization, in the country. 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